Supervisory signal apparatus for telephone-switchboards.



l Patented Mar. I2, |90I. 0. A. BELL.

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UNITED STATES PATENT ORO A. BELL, OF NEW YORK, N. Y., ASSIGNOR TO TI-IE WESTERN ELECTRIC COMPANY, OF CHICAGO, ILLINOIS.

V-SUPERVISORY SIGNAL APPARATUS FOR TELEPHONE-SWITCHBOARDS.

SPEGIFIGATION forming part of Letters Patent No. 669,501, dated March 12, 1901. Application filed July 31, 1899. Serial No. 725,627. (No model.)

T @ZZ whom, it may concern.-

Beit known that I, ORO A. BELL, a citizen of the United States, residing at New York city, in the county of New York and State of New York, have invented a certain new and useful Improvement in Supervisory Signal Apparatus for Telephone-Switchboards,(Case No. 10,) of which the following is a full, clear, concise, and exact description. l ro My invention relates to signals for telephone-switchboards, and has for its object to provide supervisory apparatus whereby the operator may inform herself as to the condition of any line or lines which may be con- I5 nected at the central office.

Generally speaking, my invention consists in the provision of a local circuit at the central oiice, associated with a connected telephone-line, a source of current, and a superzo visory signalincluded in said local circuit, means actuated in the use of the telephone at the substation for rendering said local circuit active or inactive, and thus for controlling the actuation of said supervisory signal,

z5 and switch-contacts adapted to be actuated in the use of a key, such as the operators listening-key, at the central oiiice for controlling the connection of the source of current `with the local circuit or for otherwise render- 5o ing such circuit responsive or irresponsive to current in the telephone-line.

My invention may be applied with advantage to that type of switchboard known to telephone engineers as the relay-switchboard,

3 5 and the local circuit of the supervisory signallamps may be closed through the agency of a pair of contacts in the operators listeningkey. With such an arrangement the operators listening-key is maintained depressed or 4o in condition to connect the telephone with the plug-circuit while the plugs are not in use, the supervisory signal being thus cut out of circuit to avoid waste of energy and meaningless illumination of the lamps. When the operator brings a pair of plugs into service for making a connection between two telephone-lines, her telephone is thus left in circuit until the number of the subscriber wanted has been ascertained and both plugs in- 5o serted, whereupon the listening-key is released, cutting out the telephone and bringing the supervisory apparatus into operative connection with the united lines. The key, of course, is again depressed when a disconnection is made and the plugs are returned to their places.

My invention will be more particularly described by reference to the accompanying drawing, which illustrates diagrammatically by the use of conventional symbols two tele- 6o phone-lines extending from their substations to a central office, with a pair of plugs and their connecting-circuit equipped with the supervisory apparatus of my invention.

The switchboard illustrated is of the relay type and is equipped with the usual line-signaling apparatus for indicating a call, a springjack being provided for each line, into which the connecting-plugs c c may be inserted to connect two lines together for con- 7o versation. The apparatus at the substations, as well as that which is permanently associated with each line at the central office, is well understood and needs no detailed description.

It is illustrated merely to show the application of my supervisory apparatus and will be referred to only incidentally in describing the operation of the latter.

The tip and sleeve contact portions of each connecting-plug are connected by the cord 8o conductors b c with the tip and sleeve portions, respectively, of its mate, these cord conductors being divided by a repeating-coil d, and a battery @for furnishing current to operate the subscribers transmitters is bridged across these two cord conductors between the two halves of the repeating-coil after the well-known manner of the common battery system. Two supervisory relays ff, one for each plug, are connected with the strand c of the cord-circuit, receiving current from the centralized battery e when the plugs are in use in establishing a connection, such current being controlled, as usual, by the switching apparatus, which is automatically actuated in the use of the telephones at the substations of the lines connected. The relay associated with any particular plug then will be energized when the telephone of the line with which such plug is connected is in use,

but will be deprived of current and so rendered inert when the subscriber replaces his telephone instrument on its hook and actuates his automatic switch.

In the system illustrated the armature switch-levers of each relay are connected to ground each through its own supervisory signal-lampg,and the back contacts of the relays are connected together and with a conductor h,which leads to the grounded battery t'. This battery may be the ordinary test-battery, and the conductor h maybe tapped onto the third strand Za of the plug-circuit, which unites the shanks or test-contacts of the plugs-that is, the contacts which engage with the test-rin gs of the jacks when the plugs areinserted-and which is grounded through the test-battery.

The operators listening-key Z, which is adapted When depressed to connect her telephone set fm, in a bridge across the cordstrands b c, is provided with an extra contact-spring Z. When the listening-key is in its elevated position, the said contact-spring Z is adapted to engage with a contact-point Z2, but breaks engagement with said contactpoint when the key is depressed. These two contacts Z Z2 control the continuity of conductor h, which is connected with battery fi, so that current may be supplied to the supervisory lamps g g only when the listening-key is in its elevated position, the circuit including any Ylamp being further controlled by the supervisory relay with which such llamp is associated.

The above description of the circuit connections and apparatus will, Ibelieve, be sui'- iicent foundation for a statement of the operation of the supervisory signaling apparatus of my invention without further detailed account of the particular system which I have chosen to illustrate the application of my invention.

When the connecting-plugs are in their idle condition, the listening-key is kept depressed, thus cutting 0E the battery from the supervisory circuits. Suppose that the subscriber at one of the substations should desire a connection. By removing his telephone from its hook a signal is transmitted in the usual manner, to which the operator responds by inserting one of the plugs of a pair into the spring-jack of the calling-line. Since the listening-key is normally depressed, she may converse with the subscriber immediately to learn the number of the subscriber wanted. As soon as thisinformation has been obtained the listening-keyZ is released, whereby the telephone set is cut out of circuit and the continuity of conductor h is completed at the switch-contacts Z' Z2, thus bringing the supervisory apparatus into action. The supervisory lamp of the calling-station will of course remain dark, since current from the centralized battery is afforded a path of low resistance through the calling-line, and the supervisory relay f, associated with such line, is

energized and attracts its armature, breaking the supervisory signal-circuit; but until the called subscriber responds his supervisory relay will remain inert and the circuit through his supervisory lamp will thus be completed. When the called subscriber responds, his supervisory lamp also will be extinguished, and this condition Will obtain until the conversation is finished, when the supervisory lamps of both substations will be lighted by the denergization of relays ffand the consequent completion of the supervisory circuits. The operator observing the signalfor disconnection thus given removes the plugs from the spring-jacks. Since, however, the local circuits including the supervisory signal-lam ps are dependent upon connection of the plugs with spring-jacks, but are associated only with the plug-circuits, the lamps will remain lighted until the operator depresses her listening-key and breaks the circuit that supplies current.- This she does immediately on disconnection to avoid Waste of energy and meaningless illumination of the lamps, the listening-key remaining normally depressed while the plugs are idle.

Having thus described my invention, I claim as new, and desire to secure by Letters Patent, the following:

1. A central-office apparatus for telephoneswitchboards, consisting of a plug and its cord-circuit for making connection with a telephone-line, a local circuit including a source of current and a supervisory signal, a supervisory relay connected with the plug-circuit for controlling said local circuit, an operators telephone set, a listening-keyfor connecting the same with the cord-circuit, and switchcontacts, actuated by the listening-key, for controlling the aforesaid local circuit, substantially as set forth.

2. A central-office apparatus for telephoneswitchboards, consisting of a plug and its cord-circuit for making connection with a telephone-line at the switchboard, a local circuit associated with the plug and cord circuit and independent of connection with the telephoneline, a supervisory signal and a source of current in said local circuit, a source of current for the cord-circuit and means controlled by the flow of current in the cord-circuit for rendering the said local circuit active or inactive, to display or conceal the signal, an operators telephone set, a listening-key for connecting the same with the cord-circuit= and switch-contacts actuated by the listening-key for control* ling said local circuit and rendering the sa me responsive or irresponsive to current in the cord-circuit, substantially as described.

3, The combination with telephone-lines extending from substations to a central ofce, of a pair of plugs and link conductors uniting them, for making connection between the lines, a supervisory relay associated with the pair of plugs, a local circuit, including a subsidiary supervisory signal, controlled by said relay, a source of current in the circuit, and

a manually-operated switch-key controlling IOO IIO

Igo

actuated in the use of the listening-key, a source of current, and a conductor, Whose continuity is controlled by the said switchcontacts, connecting said source of current With the local circuit, substantially as described.

In Witness whereof I hereunto subscribe my name this 14th day 0f June, A. D. 1899. 2o

ORO A. BELL. Witnesses:

H. STROBRIDGE, W. BENTLEY. 

